JP2015514535A - Self-hardening bioactive cement composition containing partially deacetylated chitin as a bone graft substitute - Google Patents

Abstract

A composition kit for medical treatment of bone healing comprising partially deacetylated chitin (PDC) having a degree of deacetylation in the range of 40-75%. The composition is provided as a kit comprising a solid fraction and a liquid fraction, provided in separate vials and mixed immediately prior to use. The weight: weight ratio of solid fraction: liquid fraction ranges from 1: 1.2 to 1: 6, preferably from 1: 1.5 to 1: 4. The solid fraction contains PDC material and calcium phosphate, and the liquid fraction contains water and acid. [Selection figure] None

Description

  The present invention is included in the field of medical treatment of fractures and bone defects and relates to compounds and compositions comprising partially deacetylated chitin and their medical use.

  Whenever there is a void in the bone due to disease or trauma, or when healing of the fracture is reduced, a common surgical procedure is to take bone from the iliac crest and transplant the bone graft to the damaged site To be done. This is called bone autograft. Autografts are used to fill the bone voids and provide the osteoinductive and osteogenic properties necessary for effective healing of the injury. This procedure is generally considered a golden standard in orthopedics, but has serious drawbacks due to the frequent morbidity associated with bone harvesting. Therefore, bone graft substitutes with osteoinductive and osteogenic properties are desired by industry and academic research institutions as well as aiming to eliminate the need for bone autografts. Such bone graft substitutes are commonly referred to as synthetic bone graft substitutes. So far, no product has emerged that has proven to provide osteoinductive and osteogenic properties substantially to bone defect injuries.

  Chitin is a natural biopolymer derived from crustacean shells, but can also be obtained from other invertebrates and fungi. Chitosan is obtained by deacetylation of the N-acetylglucosamine residue of the chitin polymer, typically by hydrolysis of the N-acetyl bond with concentrated alkali. By definition, chitosan is generally insoluble in water at a pH above 6.2, the isoelectric point of the free amine group, but is soluble in D-glucosamine (D) and N-acetyl at a pH below about 6.2. It is called a copolymer comprising -D-glucosamine (A). Typically, about 75-100% of the monomer units of conventional chitosan copolymers are D-glucosamine, which is 75-100% deacetylated chitosan or 75-100% degree of deacetylation. It is said to have (DD). Accordingly, 0-25% of the monomers in such materials are N-acetyl-D-glucosamine groups (A).

  When the degree of deacetylation is less than about 75%, chitin polymers exhibit different solubility characteristics, and such materials having a DD of about 75% to about 40% are generally partially deacetylated chitin. This is referred to as PDC in this specification.

  We have previously described the biological properties of partially deacetylated chitin polymers and oligomers. WO 03/026667 describes the use of PDC oligomers for the treatment of rheumatoid diseases. WO 2006/134614 discusses the biological properties of partially deacetylated chitin polymers and oligomers and how such oligomers act as blockers for chitinase enzymes Has been considered.

  Chae Cho et al. (J. Craniofacial Surgery Vol. 16 No 2 Mar 2005), for experiments with solid pellets containing chitosan-calcium sulfate complex and for osteogenesis of missing tibia in rabbits with chitosan with 90% DD. These effects are described.

  Yamada et al. (J. Biomed. Mat Research Vol. 66A no. 3, 1 Sep 2003, pp 500-506) investigated and discussed the effects of chitosan on biological calcification and added it to the medium for osteoblasts. The effect of chitosan was investigated.

  Klokkevold et al. (J Periodontol. 1996 Nov; 67 (11): 1170-75) evaluated the effect of chitosan on osteoblast precursor differentiation.

  WO 2004/028578 is for stimulating bone formation and bone hardening, including Bone Morphogenetic Protein (BMP) as an active ingredient in a formulation comprising a solution of tripolyphosphate and chitosan Although a composition is disclosed, the two solutions coagulate as soon as they are mixed, creating a particular concern for handling in the clinic.

  WO 01/41822 describes: (i) an aqueous thermogelled liquid component comprising dissolved chitosan and having a pH between 6.5 and 7.4; and (ii) a solid component comprising calcium. A self-gelling inorganic / polymer hybrid formulation is described, wherein the liquid and solid components when mixed together form a non-cured thermogelling composition that forms a gel at body temperature.

  WO 2006/057011 describes a solid implant consisting of a 1: 1 ratio of coprecipitated hydroxyapatite and chitosan (chitosan with 87% degree of deacetylation), and a total of 5% chitosan, calcium phosphate and Disclosed is a composition having a “putty” -like consistency comprising polydimethylsiloxane and having a solid: liquid ratio of 2: 1. The setting time of the putty-like paste was less than 6 minutes. This paste was tested for healing of induced bone damage in rats.

  In general, the art believes that chitosan itself is not osteoinductive (eg, Venkatesan and Kim, “Chitosan Composites for Bone Tissue Engineering-An Overview”) , Mar Drugs 2010; 8 (8): 2252-2266).

  There is still a strong need for further development of other more effective products that are practical for clinical applications for effective and low cost bone healing treatments.

  We have carefully investigated the biological effects of partially deacetylated chitin (PDC) polymers and oligomers and developed new and effective compositions that stimulate the regeneration of new bone tissue. did. The present invention provides a self-hardening bioactive cement material that can be injected in situ. The composition of the present invention is useful as an artificial bone graft substitute.

The composition has several practical advantages as follows.
-Natural non-toxic components without fumes or odours during mixing-Good biocompatibility and no foreign body reaction by host tissues-Less fever during curing-Relevant Can be injected and filled into voids without causing any leakage-with good moldability and injectability that allows application with minimal invasive techniques (injection)-Excess dissolution and integrity Adhesive and good wet field properties that allow for injection into a humid environment without causing loss of loss--allows adequate application time with relatively quick cure in situ Has a suitable working time-close to physiological pH and salinity when cured in situ-has good bulk capacity to allow mixing of liquid components such as blood or blood components, bone marrow or protein isolate solutions- Damaged inn Prevent scar tissue formation in bone tissue and promote regeneration of new bone tissue within the surface and void-filling composition-has advantageous antimicrobial properties, thereby minimizing the risk of infection The new compositions of the present invention use PDCs having a degree of deacetylation in the range of 40-75%, depending on the nature of the PDC, which depends on the degree of deacetylation and molecular weight. Other parameters can be appropriately optimized as described further herein.

  The composition of the present invention is provided as a kit comprising a solid fraction containing PDC and a liquid fraction that are mixed prior to use. The mixed composition comprises a low solid: liquid ratio ranging from 1: 1.2 to 1: 6, more preferably from 1: 1.5 to 1: 4.

  The present invention further provides methods for healing conditions such as bone defects and fractures.

An illustration of an apparatus for measuring stickiness / segregation. (1) Water level, (2) Cement composition, (3) Mesh net. Measurement of injection strength / resistance of compositions having different degrees of deacetylation (DD) (see Example 2). Compressive strength of the cement composition of the present invention having different degrees of deacetylation and different amounts of PDC. Standardization of mandibular volume for micro CT analysis (see Example 3). Orientation of the larger cylinder (LC) containing the entire posterior part of the mandible and the smaller cylinder (SC) containing the implanted composition. Total volume formed along the surface of the mandible of rats 7 days after implantation compared to the total volume on day 0 (0d 70 DD). Average values and standard errors of 7-8 individuals (Example 3). Cross section of rat mandible implanted with 70% DD polymer complex 14 days after surgery. This section is 1-2 mm in front of the drilled hole. The upper figure shows a paraffin section stained with H & E of the mandible. The lower figure shows a cross-section of a micro CT view of the same region of the same mandible (see Example 3). FIG. 5 is a micro CT view of an unfilled hole in a sheep left leg tibia having the composition of the present invention implanted in the right leg tibia. This figure shows cross sections of three different planes (x, y and z) 3 months after surgery (see Example 4). This figure shows how to create a virtual cylinder with a different radius concentric with the drill hole. FIG. 5 is a micro CT view of a right leg tibia implanted with a composition of the present invention on three different planes (x, y and z) 3 months after in vivo surgery. A dense calcified tissue can be seen along the surface of the composition, along with island-like calcified tissue scattered throughout the implanted composition. Calcification (per mm ³ ) inside a virtual sphere created with a radius of 2 mm inside the implanted composition of the invention (see Example 4). Bone mineralization (per mm ³ ) in virtual cylinder R3 and virtual shells R4-R3, R5-R4 and R6-R5 (see Example 4). Unfilled holes are designated E, and holes filled with the composition of the invention are designated BR. A microscopic image of an implanted composition of the present invention showing the formation of new bone within the implanted composition (see Example 4).

  The present invention provides an easy-to-use kit suitable for bone surgery that contains solid and liquid fractions that are separately packaged and sterilized by gamma irradiation. Just prior to surgery, the liquid fraction is mixed with the solid fraction to produce a liquid or pasty cement. The cement mixture can be conveniently injected into bone voids or fracture sites and has good moldability and good tack. This also allows application to bone using minimally invasive techniques such as needle injection. In other embodiments, the composition is applied to the surface of existing bone using, for example, a spatula or similar device.

  As described herein, the composition provides mechanical support to the bone defect site and stimulates osteogenic cells to exist and proliferate on the surface and within the implanted composite material. Is optimized to promote the regeneration of new bone tissue. This is obtained by creating desirable physiological conditions such as pH and salinity and controlling the solid: liquid ratio to promote cell penetration and biodegradability / resorption of the complex. The present invention has been optimized to control the physicochemical and biological properties of the implanted complex. This includes control of pH by the buffering capacity of the composition's acid (preferably phosphoric acid) and partially deacetylated chitin, control of ionic strength by careful choice of electrolyte, and the composition. One or more of control of water binding capacity / wet area characteristics and injection strength by appropriate adjustment of the degree of acetylation of the PDC polymer in the product and the relative amount of PDC can be included. Biological stimulation of osteogenic cells is obtained by in situ hydrolysis of PDC by endogenous family 18 chitinases expressed by various cells of the immune system. This is supported by our data further illustrated and described in Example 3 (see “Results” in Example 3). This results in the sustained release of biologically active molecular species of PDC oligosaccharides. Thus, these oligomeric molecules are gradually released as the composite material degrades, diffuse into adjacent tissues, provide persistent stimulation to osteogenic cells, and invade the degraded complex This is then replaced with new bone tissue. The solid: liquid ratio plays an important role in optimizing this entire process.

  Thus, in order to optimize the above properties, it is surprisingly advantageous that the mixed composition includes a low solid: liquid fraction ratio in the range of about 1: 1.2 to about 1: 6. I understood. This corresponds to a range of about 14% to 45% by weight of the solid fraction in the combined mixture. The composition is not limited, but is 1: 1.2, 1: 1.33, 1: 1.5, 1: 1.8, 1: 2, 1: 2.25, 1: 2. A ratio of about 1: 1.3 to about 1: 4 or a range of about 1: 1.3 to about 1: 3, more preferably about 1: 1, including ratios of .5, 1: 3 and 1: 4. It is preferred to have a solid: liquid fraction ratio in the range of 5 to about 1: 3, for example in the range of about 1: 2 to about 1: 3 (these ratios are 44 in a combined mixture). Corresponding to the weight content of the solid fraction of 4%, 42.9%, 40%, 35.7%, 33.3%, 30.8%, 28.6%, 25% and 20%).

  Cement compositions having a preferred solid: liquid (S / L) ratio have good tack in the human body (little segregation) and good wet area properties with minimal dissolution, which is Means that it maintains its integrity and does not diffuse from the injection site. This provides a good cavity filling capability including infiltration into a spongy and porous bone with initial long term adhesion to bone tissue. Although a low S / L ratio may reduce the mechanical strength of the cement, optimization of the S / L ratio and chitosan content promotes faster cement degradation and makes cells more efficient into composites Allows the use of osteogenic PDC and hydroxyapatite for rapid penetration and early initiation of bone regeneration. Thus, the low initial mechanical strength is compensated by the early onset of bone formation and subsequent accumulation of new bone, and mechanical loads are quickly absorbed.

Mechanical strength can be evaluated in several ways, some of which are described in the accompanying Example 1. In a particular embodiment, the composition of the invention is in the range of 0.2-10 N / mm ² after being placed in physiological saline (0.9% NaCl) at 37 ° C. for 24 hours, eg 0.5 It has a mechanical strength measured as an ultimate compressive strength in the range of -5 N / mm ² or in the range of 0.5-2.5 N.

  Due to the desired low S / L ratio of the composition, the hardened cement composite of the present invention has a significant content of free water, which means that the formed composite graft material has communicating holes. It shows that. Accordingly, the composition of the present invention, in a preferred embodiment, is in the range of about 40-90%, more preferably in the range of 40-70% by weight, for example in the range of 50-70% by weight, for example in the range of about 55-65% by weight. More preferably in the range of about 60-65% by weight, for example about 60% by weight of free water after curing (water released by drying at 105 ° C. for 24 hours). These values refer to the free water content measured in cement formed in vitro and formed in saline (0.9% NaCl) for 24 hours. In general, the lower the S / L ratio, the greater the amount of moisture loss during drying of the cured composite. As an example, an S / L ratio of 2 can result in a loss of water of about 60 ± 5% of the cured wet weight.

  Loss of stickiness / solubility or integrity can be assessed in various ways. We place an amount of the freshly mixed composition on a mesh net (eg, about 1 mm mesh) below the liquid level in a beaker containing saline (stir with a magnetic bar). We have found it useful to evaluate this property (see further description in Example 1). After a short period of agitation, such as 10 minutes, substantially all of the material is still adhered, such as greater than 95%, more preferably greater than 98%, even more preferably greater than 99%, and most preferably greater than 99.9%. Preferably it is.

  The mixed cement composition preferably has a pH close to neutral, or a range of about 6.0 to 7.8, more preferably a range of 6.5 to 7.4, and most preferably about 7. . The solid fraction containing calcium phosphate is generally substantially alkaline, while the liquid fraction is typically acidic to neutralize the alkaline phosphate. In a preferred embodiment, the liquid fraction is one or more acids selected from, but not limited to, phosphoric acid, hydrochloric acid, ascorbic acid, lactic acid, acetic acid, citric acid, formic acid, propionic acid, malic acid and glutamic acid. including. The preferred concentration / amount of acid sufficient to neutralize the mixed composition depends on the S / L ratio of the composition, the amount of phosphate and the DD of the PDC. If a lower S / L ratio (less solids) is used, less acid is required. A preferred acid in this embodiment is phosphoric acid. In a preferred embodiment, the liquid component comprises at least about 5% phosphoric acid, such as about 2.5-20% by weight phosphoric acid, such as 2.5-15% by weight or 5-15% phosphorus. Acid, such as about 5%, about 8%, about 10%, about 12% or about 15% phosphoric acid. In other useful embodiments, the liquid fraction includes one or more other acids, such as any one or more of the above acids, instead of or in addition to phosphoric acid. In these embodiments, the total amount of acid is preferably sufficient to render the solution substantially neutral after mixing the alkaline solid fraction with the liquid fraction. Accordingly, the acidity is preferably at least the same as that of a 5% phosphoric acid solution. Accordingly, it is appropriate that the liquid fraction has a pH in the range of about 1 to 2.5, more preferably in the range of about 1 to 2. In other embodiments, acidity can be achieved by providing in the liquid fraction an acid having a normality (N) equivalent to 5% phosphoric acid solution or higher acid strength as described above. .

  The PDC itself also has a buffering capacity, so conventional calcium phosphate self-hardening composites exhibit a faster and less controllable pH drop during curing compared to the preferred compositions of the present invention. The presence of PDC means that PDC can consume (neutralize) the remaining hydrogen atoms during the formation of hydroxyapatite, thereby suppressing changes in pH.

  Thus, when other acids are used in addition to or instead of phosphoric acid, more calcium phosphate may be required to obtain sufficient phosphoric acid content. The acid content of the composition thus obtained in the overall composition after mixing the solid and liquid fractions is at least about 2.0% phosphoric acid, or an equivalent amount with or without phosphoric acid. Other acids are preferred, such as phosphoric acid in the range of about 2.5-25%, for example in the range of about 3.5-15% or 5-10% or the like.

  The composition of the present invention has good injectability. The optimal injection strength for injecting 2-3 mL of the new cement composition of the present invention with a 5 mL syringe (B. Braun or equivalent) with a 12 mm inner diameter and a 2 mm outlet is preferably about 10-30 N. , More preferably about 20 N or less, more preferably less than about 15 N or less than about 10 N. This can be measured as described in Example 1.

  The composition of the present invention includes PDC incorporated into the solid fraction, which has an important role in curing the cement. The higher the degree of deacetylation (DD), the shorter the curing time. On the other hand, curing is related to temperature, ie the higher the temperature, the shorter the curing time. Accordingly, a PDC having suitable parameters may be selected, thereby optimizing the composition according to actual surgical needs and adjusting the cement setting time. The cure time achieved at room temperature (20-25 ° C.) using 50% DD PDC is 30 minutes, but below 5 ° C., the cure time may exceed 3 hours.

  The term cure time as used herein refers to cement to the extent that it cannot be easily applied as described herein, and can no longer be molded without breaking. Refers to the time when is cured.

  Another useful term is working time or use time, which is the time from initial mixing (and a short waiting time for the composition to become fully sticky) to the time to reach cure time. Refers to the time that the composition can be worked / used. For the compositions of the present invention, the usable time at room temperature (20-25 ° C.) is preferably 2-25 minutes from the initial mixing, for example 2-20 minutes or 3-20 minutes from mixing. . This can vary greatly depending on the exact composition and operating room temperature. In general, the lower the S / L ratio of the composition, the longer the period of waiting for the start of the working time, such as in the range of 3-8 minutes, for the S / L ratio in the range of 1: 2 to 1: 3. This is offset by later cure time. Thus, when the S / L ratio is 1: 1.5, the working time at room temperature is generally about 2 minutes to about 9 minutes from mixing, but when the S / L ratio becomes lower, such as 1: 2. , The working time lasts from about 6 minutes to about 20 minutes from mixing, and therefore the use time is longer. If even lower S / L values are used (eg 1: 2.5 or 1: 3), the working time will change further and start slower from mixing, but the composition can work for longer periods of time. It remains.

  The desired mechanical strength is typically achieved by adjusting the relative amount of PDC, which is very heavy for the mechanical properties of the cement. The cement reaches peak compressive strength at about 20 w / w% PDC of the total cement. In general, cements containing 50 w / w% PDC can be prepared. The composition of the present invention, in a preferred embodiment, is 10% or less by weight of the total weight of the combined composition (solid and liquid fractions), for example about 2-10 of the combined fraction. %, In some embodiments in an amount in the range of about 2.5-5%.

  Furthermore, the amount of PDC in the cement composition affects the osteogenic effect when applied in bone voids or fracture sites, the higher the amount, the higher the osteogenic effect. Become.

  In the composition of the present invention, the solid fraction preferably contains PDC in the range of 3 to 30% by weight, and the cement containing PDC exceeding the above amount causes excessive bone growth depending on the degree and pattern of acetylation. May be induced. More preferably, the solid fraction comprises PDC in the range of 5-15% by weight, for example in the range of 5-10%.

  The PDC in the composition of the present invention preferably includes a regenerated polymer that is subjected to dissolution and subsequent filtration of impurities to remove endotoxin from the matrix and then dried in a suitable drying process. To do. This regenerated chitosan, in other embodiments, is substantially pure and has a similar degree of deacetylation, molecular weight and particle size, or partially deacetylated if the contained endotoxin is at a low concentration. It may be replaced with a modified chitin. Furthermore, in certain embodiments of the invention, chemically modified PDCs such as quaternary chitosan, carboxymethyl chitosan or other salt forms or other forms may be used for cement formulations.

  The PDC in the composition of the present invention is preferably a highly purified PDC having an endotoxin concentration of less than 100 EU / g. This ensures good biocompatibility of the cement and provides an osteogenic effect instantly upon contact with bone tissue.

  As already mentioned, the PDC material used in the present invention is in the range of 40-75%, more preferably in the range of about 40-70%, in the range of about 40-60% (eg about 40%, about 45%). %, About 50%), or a range of about 50-60% (eg, 55% or 60%).

  Furthermore, the PDC minimizes the presence of block N-acetyl-D-glucosamine (A) or D-glucosamine (D) moieties such as AAAAA or DDDD. Thus, it is preferred that it be deacetylated in a random form during the deacetylation process (ie, deacetylation of chitin, which is a preferred method of obtaining chitin derivatives suitable for the present invention). When hydrolyzed by endogenous chitinase in the body, such desired semi-randomly deacetylated material allows optimal length with respect to its amount, molecular weight, family 18 chitinase blockade and affinity for chitinase-like proteins. Thus, an optimal therapeutic target for bone tissue regeneration is obtained.

  The degree of deacetylation and the distribution of the remaining acetyl groups has a significant impact on the osteogenic activity of PDC polymers and oligomers. The less deacetylation, the more homogeneous the distribution of acetyl groups and the higher osteogenic activity is shown by PDC. In a preferred embodiment of the present invention, it is preferred that the distribution is semi-homogeneous, i.e. neither the distribution of the acetyl groups as described above nor a completely homogeneous and uniform distribution. N-acetylglucosamine residues means that 100% should not be distributed like all other monomers).

  As used herein, the molecular weight (MW) of PDC refers to the weight average molecular weight of the PDC polymer. The MW of the PDC affects various properties of the composition, such as mechanical strength, injectability, moldability, tackiness or segregation, filling ability, and curing time. The preferred effective MW is in the range of 10 to 1000 kDa, therefore the preferred MW of PDC in the composition of the present invention is within the above range. Formability and segregation properties improve with increasing MW, but very high MW may not favor the injectability and fillability. In the composition of the present invention, the preferred range of the chitin material is in the range of 30 to 200 kDa.

  A mixture of high and low MW may contain various conflicting properties, such as injection properties for segregation properties. On the other hand, the healing process may be shortened by the incorporation of an oligomeric form of therapeutic PDC. In certain embodiments, the composition typically has an oligomer length consisting of about 3-12 sugar residues in the oligomer chain and about 5-25% by weight of the total content of the PDC material (eg, about As part of the PDC material (such as 5%, 10% or 15%), partially deacetylated chito-oligomers having DD values in the range of about 30-70% are included. This promotes early initiation of bone formation.

  After preparing and packaging the kit, it is preferable to sterilize by gamma irradiation. Since gamma irradiation can affect the MW of the first PDC material, the first PDC material in the composition before irradiation has a MW in the range of 200-1000 kDa, and by irradiation, after gamma irradiation The final MW may be 30 to 200 kDa. The effective initial MW may in some embodiments range from 10 to 1500 kDa, and the final MW may range from 10 to 1000 kDa. The most preferred range for the final MW is the range of 30-200 kDa, as described above, so the preferred initial MW range is 20-20 when measured by a GPC / SEC system using a light scattering detector. A range of 1000 kDa, for example, a range of 100 to 1000 kDa, more preferably a range of 200 to 1000 kDa.

  The effective dose of gamma irradiation is preferably in the range of 9-100 kilogray in the context herein, and the optimum preferred dose is in the range of 20-35 kilogray.

  Preferably, the PDC in the composition of the present invention has a particle size of 500 μm or less. In an acidic environment, such materials dissolve quickly and react with calcium phosphate to adjust cement properties.

  As already mentioned, the present invention has a PDC incorporated into the solid fraction. This has the further advantage of avoiding acid degradation that may occur during storage. This ensures a reasonable shelf life of the cement and avoids both degradation of cement properties and economic loss.

  The solid fraction of the composition also contains calcium phosphate. In a preferred composition of the invention, calcium phosphate forms a low crystalline precipitated hydroxyl apatite to ensure optimal anabolism and to form bone tissue in the body.

  Preferably, the solid fraction of the composition comprises acidic calcium phosphate and basic phosphate. When mixed with the liquid fraction and neutralized, calcium phosphate causes the formation of precipitated hydroxyl apatite. The most preferred ratio of calcium: phosphate, the Ca / P ratio, is in the range of about 1.6 to 1.7, while the Ca / P ratio is the preferred range according to the present invention, 1.2 to 2.2. It is effective in the range.

  Thus, in one aspect, the calcium phosphate is α-tricalcium phosphate and tetracalcium phosphate. These preferably have a purity of more than 80% (according to our experience, a purity of less than 80% can also be used and cannot result in degradation of osteogenic properties). Other combinations of calcium phosphate that cause the formation of hydroxylapatite may also be used in the present invention.

  Because calcium sulfate is brittle and exhibits lower strength than calcium phosphate, it tends to have a faster resorption rate in the body than calcium phosphate. A mixture of calcium sulfate and calcium phosphate can have the advantage of combining both the resorption rate and mechanical properties of cement in the body.

  The calcium phosphate preferably has a particle size of 180 μm or less, more preferably less than about 100 μm. Mechanical strength is inversely proportional to particle size. The most preferable size is 50 μm or less.

  In some embodiments, the composition comprises sodium glycerophosphate in the solid fraction. Sodium glycerophosphate may be used to further enhance the mechanical properties of the cement and adjust the cement salinity to physiological conditions.

  In other embodiments, other phosphates can be used in place of, or in addition to, sodium glycerol phosphate such as sodium hydrogen phosphate, disodium hydrogen phosphate.

  As mentioned above, the present invention further provides a method based on the use of the composition of the present invention for healing a fracture. The method comprises the steps of providing a solid fraction and a liquid fraction as described above, and combining the two fractions with a solid fraction: liquid fraction ratio ranging from about 1: 1.2 to about 1: 6. More preferably mixed together in the ranges described and defined herein above, for example, most preferably in a ratio of about 1: 2. The two fractions are mixed and the mixture is allowed to cure for a suitable time until the desired consistency and viscosity are obtained, at which time the “working time” of the composition begins and then healing is desired. The mixture is inserted into the fracture site, preferably by injection. The handling of the composition is well suited for clinical procedures involving orthopedics. Use this product in place of bone grafts when filling bone voids to promote healing in fracture healing, spinal fusion, osteotomy, eg periodontal surgery, bone cancer surgery, eg Healing can be promoted in limb-preserving surgery, reconstruction of bone fusion failure in peripheral bone, and repair of osteolytic processes in benign processes.

  Thus, the present invention is described herein, which is generally used as a drug for bone repair and healing, particularly when a PDC is provided in a composition kit as described herein. Such PDC materials are also provided.

Example 1: 1 Material Properties of Specific Compositions of the Invention Having a S / L Ratio of 1: 2 The solid and liquid components are mixed separately and brought together and mixed with a spatula just prior to use.

  Texture: The cement composition immediately after mixing has a milky white paste texture at the start of the working time. In the range of 15-30 N, 5 mL of B.P. Injection strength is measured using a Braun syringe (12 mm inner diameter and 2 mm outlet).

  The working time of the composition at room temperature (20-25 ° C.) is in the range of 3-25 minutes from the initial mixing, ie 25 minutes at room temperature, but 3 ° C. with a curing time of up to 3 hours. is there.

  The initial pH when 7.4 g of this composition was placed in 5 mL of unbuffered saline (0.9% NaCl) was 7.4. The pH after 6 hours was 6.84, 6.47 after 1 day and 5.94 after 5 days.

  The tackiness of this composition was measured as follows.

  In a 100 mL beaker with a 2.5 cm magnetic stirrer at the bottom and a 25 mesh net placed 1 cm deep from the surface, 50 mL of saline (0.9% NaCl) is placed. 0.5 ml of ready-to-use cement is injected over the mesh (in a circular motion that will result in a “spiral ring” shape). The apparatus is shown in FIG. The solution is stirred for 10 minutes at a speed of 100 rpm. The exact weight of the injected cement is determined (by weighing the syringe before and after injection). After the stirring period, the solution is transferred to a turbidity measuring tube and the turbidity is measured and expressed in NTU.

  Calibration curve: Stock suspensions were prepared using each cement as a standard. The weighted portion of the cement (0.0000 g accuracy) was dispersed throughout to produce a turbidity of 1000 NTU. Standard suspensions with 0, 200, 400, 600, 800 and 1000 NTU were prepared by serial dilution using the stock suspension. A linear graph was prepared in which the amount of cement was plotted against the turbidity of the suspension. In this way, the turbidity of the test solution was measured after 10 minutes of stirring to determine the amount of cement dispersed.

  This measurement revealed that less than 0.1% of the cement composition was segregated and dispersed in saline.

Further mechanical properties:
A needle (3 mm outer diameter) was pushed into a fully cured composition embedded in a 96 well plate (φ6.7 × 13 mm) to a depth of 5 mm and the penetration resistance was measured with a load cell. The composition was cured in saline (0.9% NaCl) at 37 ° C. for 24 hours. Using the MTS test apparatus (MTS Insight 10, Eden Prairie, Minn., USA) using 6-8 replicates for each composition, the compositions described in Table 1 (S / L ratio = The measured resistance of 1: 2) was 8.08 ± 0.34 N / mm ² .

The penetration of compositions having various S / L ratios was also tested. A composition having an S / L ratio of 1: 1.5 has a penetration resistance of 17,25 N / mm ² , which is a composition having an S / L of 1: 2 (6,221 N / mm ² ). And the measured penetration resistance of the composition having a 1: 1 S / L ratio was 32,82 N / mm ² .

  The strength of the cement is calculated from the penetration force at a displacement of 5 mm. Previous experiments have shown that there is a linear correlation between the penetration test and the classical compression test (CCT).

Example 2: Effect of deacetylation on mechanical properties Injection strength: two compositions as described in Example 1 except that two different DD values are used, ie 50% and 70% PDC Was prepared. Using an MTS testing apparatus, B. with a 12 mm inner diameter and a 2 mm outlet. The injection test was performed with a Braun 5 ml syringe. The results are shown in FIG. 1 (tests were performed at either 25 ° C. or 3 ° C., see FIG. 2).

  Compressive strength: Similar to Example 1 except that three different DD values were used, i.e. 40%, 70% and 94%, and a PDC having an S / L ratio of 1 was used. Prepared. The compressive strength was tested using a 500 N load cell with a crosshead speed of 20 mm / min using an MTS test apparatus. Initial cement temperature was set at 3 ° C. and 25 ° C. during the test. The results are shown in FIG. Five samples were used for each treatment in the compression test and each size was φ9.6 × 15 mm. These specimens were cured in saline (0.9% NaCl) for 24 hours at 37 ° C. for curing and the test conditions were as described for the injection test.

Example 3: In vivo testing of the composition in the rat mandible model-optimization of the degree of deacetylation
Introduction :
The rat mandible (mandible) is a frequently used model for bone healing studies (Bone repair in rhBMP-2 associated with two carriers) Bone formation in trabecular bone cell seeded scaffolds used for reconstruction of the rat mandible; Micron, Volume 39, Issue 4, June 2008, Pages 373-379, Joao Paulo Mardegan Issa et. (Bone formation in skeletons seeded with cancellous bone cells used for rat mandibular reconstruction); International Journal of Oral and Maxillofacial Surgery, Volume 38, Issue 2, February 2009, Pages 166-172, H Schliephake, et.al., Bone regeneration in the rat mandible with bone morphogenetic protein-2: A comparison of two carriers (Bone regeneration in the mandible of rats using bone morphogenetic protein-2: comparison of two carriers); Otolaryngology-Head and Neck Surgery, Volume 132, Issue 4, April 2005, Pages 592-597, Oneida A. Arosarena, Wesley L. Collins; Spontaneous bone healing of the large bone defects in the mandible; International Journal of Oral and Maxillofacial Surgery, Volume 37, Issue 12, December 2008, Pages 1111-1116, N. Ihan Hren, M. Miljavec).

  The mandible is a metabolically active bone that responds to constant stress caused by eating and biting. We have developed an animal model for severe bone lesions in the mandible of rats using micro CT analysis to measure new bone growth and osteogenic response, and calcification of micro CT diagrams Histological examination was performed to convert the feature points into calcified bone tissue. A 4 mm diameter drill hole is drilled in the central region of the rat jaw masseter fossa to obtain a severely sized void that affects the mechanical properties of the bone (FIG. 4). This makes it possible to compensate for weakening of the bone structure by activating an appropriate osteogenic response in response to the damage of the bone. Micro-CT analysis can quantify calcification using a defined portion of the mandible (FIG. 4). This has been found to be an excellent means for evaluating the osteogenic effect of biomaterial injected into this void as a bone graft material. In this study, the model is used to evaluate the bone growth stimulating effects of different derivatives of chitin in calcium phosphate-based injectable bone void fillers. These chitin inductions can be attributed to three types of chitin polymers with different degrees of deacetylation: 50%, 70% and 96% deacetylated chitin polymers and one 50% deacetylated oligomer (T-ChOS). (Trademark), Genis, Iceland). Based on our previous rat jaw study, the implantation time was adjusted to 7 days. The acetylation of this polymer appears to be important for inducing new bone formation, and it has been found that the 50 DD polymer is the most active and the 96% DD polymer is inactive.

Materials and Methods The chitin derivatives used in this study were as follows:

  50DD PDC: Deacetylation degree 50% (same material as described in Table 1).

  70DD PDC: Deacetylation degree 70%.

  96DD chitosan: 96% deacetylation.

  50DD oligomer (T-ChOS ™, Genis, Iceland): T-ChOS ™ contains no monomers and contains less than 10% dimers and trimers. Octamers are oligomers that are most abundant in the composition.

  The average molecular weight of all polymers was over 130 kDa as judged by size exclusion chromatography.

  A kit was prepared containing four different implant composites, each containing a solid component (solid fraction) and a liquid component (liquid fraction). The solid component (one tube) consists of 0.155 g chitin derivative, 0.904 g tetracalcium phosphate and 0.701 g α-tricalcium phosphate, 0.220 g sodium glycerophosphate and 0.098 g hydroxylated. It contained calcium (total weight of the solid fraction was 2.078 g). The liquid component (one tube) contained 0.398 g phosphoric acid and 3.504 g water (total weight 3.902 g) (S / L ratio 1: 1.88).

  One solid component and one liquid component were placed in an aluminum laminated heat sealed plastic bag to produce a kit that was completely ready for use. All kits were sterilized with gamma irradiation (20 kilo gray, Radiation Center, Oregon State University, USA).

  During surgery and prior to implantation, these components were mixed aseptically, placed in a syringe and maintained at 4 ° C. until implantation.

  The test animals were male Sprague-Dawley rats (260-280 g) supplied by Taconic, Denmark. Upon arrival, the animals were clinically examined and kept acclimated to the laboratory facility for 30 days prior to surgery. The average body weight of the animals on the day of surgery was 413 g and ranged from 430 to 464 g. Experiments were performed under permission (license number: 0709-0405) issued by the Icelandic Commission for approval of animal experiments. Surgery was performed by orthopedic surgeons and anesthesiologists, and drug dosage and animal protection were supervised by a veterinarian.

  Each animal's left jaw was shaved and disinfected to prepare for surgery. The mandible was accessed through an incision located above and parallel to the lower edge of the mandible. The masseter fossa was accessed by blunt atraumatic incision of the masseter fibers. Using a 4 mm dental drill, a 4 mm hole was made in the center of the masseter fossa. After thorough rinsing with sterile saline (5 ml), 25 μl of the experimental test formulation was injected into the hole using an Eppendorf dispenser or left untreated (unfilled void control). . The surgical wound was closed with a suture.

  A total of 6 groups were established using 39 animals. Table 2 shows the experimental design.

  At the end, rats were anesthetized with isoflurane and bleed from the heart terminally under anesthesia. The left jaw was then dissected to release from the temporomandibular joint and placed in 3.7% formaldehyde in 50 mM phosphate buffer (pH 7.0).

  Scanning was performed with a micro CT scanning device (Nanotom manufactured by General Electric Inspection Technologies). The sample was fixed in a sealed plastic cylinder filled with a fixing solution and mounted on a rotary table of a CT scanning apparatus. For comparison of gray values, scanning was performed using an Al phantom and a plastic phantom (PET) as reference points. The magnification is 4 times, the voxel size is 12.50 μm / voxel edge, the number of collected images is 1080 (step angle: 0, 33 °), the exposure time is 2000 ms, the average number of frames is 3, and the number of skipped frames is 1 The X-ray settings were 100 kV, 125 μA using 0 tube mode and no filter.

  Three-dimensional image reconstruction was performed using the Datas-x software attached to the CT scanning device. Data analysis was performed using Volume Graphics Studio Max 2.0 manufactured by Volume Graphics.

  Volume of the cylinder containing the entire bone extending posteriorly from the distal edge of the last molar, including mandibular processes, angular processes, ridges and holes with or without graft material (Fig. 3, LC). The definition of gray value truncation value / gray value determined the total bone volume (old and new bone) contained in this volume and the graft material. In the case of a jaw containing the implant material, the smaller cylinder was defined perpendicular to the larger cylinder containing the implant material (FIG. 3, SC). The volume of graft material contained in this cylinder was subtracted from the total volume of bone and graft material determined by the larger cylinder. In this way, an estimate of the total bone (new and old bone) volume of the treated and untreated jaws was obtained (FIG. 3).

  Samples were placed in buffered fixative after micro CT scan. Selected samples were decalcified for 3 hours with Decalc (Histolab, No. 00601, Göteborg, Sweden). The specimens were then dehydrated, embedded in paraffin, sliced (2 μm) and stained with hematoxylin-eosin. The slices were examined and photographed using an optical microscope (Leica DM 2000, Germany) connected to a digital camera (Leica DFC 290).

Results Within 7 days, induction of acetylated chitosan resulted in an increase in the volume of calcified jawbone (FIG. 4). For each group, the average calcified bone volume (AMBV, unit: mm ³ ) was calculated (mean ± standard error). No significant difference was observed between the two control groups (unfilled void group and zero day group, 69.4 ± 3.1 and 71.1 ± 2.3, respectively, FIG. 5). AMBV is negatively correlated with the% DD value of the deacetylated chitin polymer, with the mean value of the 96DD group being 71.9 ± 2.9, the 70DD group being 84.2 ± 4.5, and 50DD. The group was 87.3 ± 3.8 (FIG. 5). Compared to the unfilled void group, the AMBV in the 70DD and 50DD groups was significantly increased (18% and 23%, respectively). Interestingly, the 96DD group (96% deacetylated chitosan) has no significant effect on calcified bone volume (FIG. 5).

  The oligomeric complex (T-ChOS ™ graft material) induced an 11% increase in bone volume (FIG. 5). This induction was significant (p <0.05). However, due to the decline in physiochemical properties, T-ChOS ™ implants were often chewed and holes were lost. This was evident when examining the micro CT scan image. Most of the T-ChOS ™ implant was missing from the drilled hole. The polymer is clearly essential for the mechanical stability of this bone cement formulation.

  FIG. 6 shows a histological micro CT cross-sectional comparison of the mandible of the same rat 14 days after implantation of an injectable composition based on a 70% DD polymer. This section is 1-2 mm in front of the drilled hole. Calcified tissue (A, B, and C) considered as new bone by micro CT analysis appeared as newly formed bone tissue as judged by the hematoxylin-eosin stained part.

  As judged by micro CT and histological examination, the density of all new bones was lower than the original jawbone. Tissue preparations revealed formation of cancellous bone with angiogenesis within new bone growth. New bone growth always occurred from the periosteum covering the outer surface of the bone, not from the bone defect site itself (FIG. 6). Thus, it can be said that this PDC-induced bone growth was localized distally from the drilled hole across the surface of the mandible, mainly along the site exposed to the maximum mechanical stress inside the jaw. . This can only be explained by the activity of small molecules that can diffuse throughout the tissue associated with bone. These small molecules are most likely PDC oligomers formed by in situ hydrolysis of the PDC polymer in the implant material. This hydrolysis is most likely catalyzed by family 18 chitinases expressed by leukocytes (neutrophils and macrophages). These active chitinases cleave partially acetylated chitin polymers to form PDC oligomers of various sizes. These said PDC oligomers diffuse from the implanted composition into the adjacent tissue and catalyze this distal bone growth promotion in response to mechanical stress on the bone.

Example 4: Treatment of severe bone voids in the proximal sheep tibia The compositions described in Example 1 (Table 1) and Example 2 were treated with 45 5 year old sheep (5.83 ± 0). .71 years old, mean ± standard deviation) transplanted into the epiphysis of the proximal tibia and tested. All sheep were operated in the same way, 15 were raised for 3 months for short-term evaluation and 15 were raised for 13 months for long-term evaluation. This experiment was performed under permission (license number: 0709-0405) issued by the Icelandic Commission for approval of animal experiments. Surgery was performed by orthopedic surgeons and anesthesiologists, and drug dosage and animal protection were supervised by a veterinarian.

Mixing of liquid and solid components The partially deacetylated chitin polymer used in this sample had the following properties: 50% degree of deacetylation, 1% solution of 1% acetic acid 100% solubility in, solution viscosity of 460 cP, turbidity in solution below 10 NTU, apparent average molecular weight of 330 kDa, endotoxin content of 93 EU / g.

  The solid and liquid components of the kit were placed in a sterile plastic cup, stirred and kneaded together for 2 minutes with a sterile spatula to form a viscous slurry.

A hole 8 mm in diameter was drilled in the middle of the surgical bone's leading and trailing edges at the rough surface height of the left and right tibia of each animal. The entrance hole was drilled at a right angle into the cortex, then the drill was redirected 45 ° upwards and drilled below the bottom of the upper surface of the tibia (plateau). The drill was not cooled during the drilling procedure. After making a hole with a drill, the bone debris was thoroughly washed away from the hole of the drill by rinsing with 40-50 mL of sterile physiological saline and sufficiently sucking. After mixing the liquid and solid components of the test kit, 1.5 mL of the slurry is placed in a 5 ml sterile syringe fitted with a sterile pipette tip, and the material is removed from the tibial plateau below and outside the opening in the cortex. Until then, the entire contents were injected into the drill hole to ensure that the entire drill hole space was filled and expanded. The left leg hole was left unfilled and used as a negative control. The surgical wounds on both legs were then closed with 4-0 Vicryl continuous subcutaneous suture and the skin closed with 4-0 Etilone continuous intradermal suture. After waking up after surgery, the animals were returned to the sheep fence for recovery where they were carefully monitored until they were ambulatory.

Post-mortem treatment of the sample Immediately after explantation, the bone sample is placed in a 50% phosphate buffer (pH 7.0) of 3.7% formaldehyde and then, together with a hydroxyapatite phantom standard, a micro CT scanning device (General Scanning was performed with a Nanotome manufactured by Electric Inspection Technologies. To obtain data from the zero time point, cylindrically shaped samples prepared in vitro and cured in physiological saline at 37 ° C. for 24 hours were also scanned. After scanning, the bone samples were sawed into 4 mm thick sections, returned to the buffer fixative and left for a further 4 weeks. After the fixation period, the sample was placed in a neutral pH 15% EDTA solution for decalcification for up to 4 months with periodic renewal of the EDTA solution. After decalcification, samples were prepared for histological examination (paraffin) and stained with hematoxylin and eosin.

Micro CT Analysis Primary micro CT data was subjected to 3D image reconstruction and data analysis using Datato-X software and Volume Graphics studio Max 2.0 from Volume Graphics. The reconstructed three-dimensional image included the entire pituitary gland that spanned 3 cm below the tibial plateau from the drill hole and all possible implants that could exist outside the drill hole. The gray value truncation value / gray value definition determined the volume of old bone, new bone and graft material in this reconstructed 3D image. A higher concentration of hydroxyapatite within the standard appears in the micro-CT image with a lighter grayscale value ("whiter"). Since hydroxyapatite is the main component of calcified bone that induces X-ray attenuation, the grayscale value of the reference material can be used to infer the degree and distribution of calcification in the sample. By comparing the hydroxyapatite standard and the gray scale value of the sample, the degree of calcification can be determined. The brightest region in the CT image indicates the tissue with the highest degree of calcification.

For quantitative evaluation, a virtual cylinder with a length of 4 mm and a radius of 3 mm was defined, and the axis of the cylinder was carefully aligned with the longitudinal axis in the direction of the drill hole (FIG. 7). While keeping the direction of the cylinder fixed, its radius was gradually increased to 4 mm, 5 mm and 6 mm, and the inorganic volume in each cylinder was measured. This analysis was repeated for all samples, both in the unfilled hole (left tibia) and the hole containing the graft material. Pull the narrower cylinder from the wider cylinder, such as radius 4mm to radius 3mm (R4-R3), R5-R4, and R6-R5, and the 1mm outer shell (tube) mineral of each cylinder The volume of the phase was obtained. The volume of the mineral phase of all cylindrical shells was normalized to a standard volume of 1 mm ³ to obtain mineral density, and this data was analyzed statistically using SigmaStat and SigmaPlot software.

Results Cross-sectional micro-CT images showing the implanted material and surrounding tissue in three planes were generated from all samples. These images were used for visual assessment to define a virtual cylinder used for quantitative assessment of mineral density.

  Tissue sections were used to assess tissue response to the transplanted material with emphasis on signs of inflammation, foreign body reaction, scar tissue formation and newly formed bone tissue.

Interpretation of micro CT data
After 3 months in vivo, visual assessment revealed a clear new bone dense shell well bound to the adjacent cancellous bone tissue around the graft material. The island-like dense structure inside the implant material showed bone formation scattered throughout the material (FIG. 8). After 13 months in vivo, this becomes even more pronounced, the surrounding shell appears to be thicker, and the formation of bone in the graft material is even more than in 3 months in vivo. It was remarkable.

  Statistical evaluation of mineral density in Ex vivo and in vivo samples showed a 21% decrease in mineral density over 3 months in vivo. Between 3 and 13 months in vivo, the mineral density of the graft material increased again by 33% (Figure 9).

  At 3 and 13 months, there appeared to be no calcified tissue growth in the unfilled holes. However, a thin shell of dense bone tissue appeared to surround the unfilled hole. This was found by quantitative evaluation of R4-R3 data (FIG. 10). This revealed that the 8 mm drill hole was a serious bone fracture in this model.

  Gray value distribution was measured at 3 and 13 months to quantify graft material and bone changes using Matlab (MATTRIX LABoratory) software and medical imaging segmentation software (MIMICS) . The results demonstrate a significant difference in gray value distribution between the 3 month implant material and bone. However, at the 13th month, the gray value distribution of the transplant material changed and became similar to the gray value distribution of the surrounding bone. These results suggest a morphological change of the transplant material for 10 months, indicating that the transplant material gradually converted into bone tissue.

Histological evaluation of the tibia 3 months after confirmation by histological analysis revealed that the graft material was completely biocompatible with no signs of inflammation or foreign body reaction. Scar tissue formation was negligible. A new bone tissue shell that was tightly integrated into the adjacent cancellous bone appeared to surround the entire graft material, and the island-like new bone was scattered throughout the graft material (FIG. 11). A region of tissue slice image aligned with the corresponding image of the micro-CT section surrounding the transplant material and characterized by high density (highest x-ray attenuation) scattered throughout the transplant material is the newly formed bone Confirmed the organization.

Claims (23)

A composition kit for medical treatment to heal bones,
a. A solid fraction comprising partially deacetylated chitin (PDC) and calcium phosphate having a degree of deacetylation in the range of 40-75%;
b. An acidic liquid fraction containing water and acid;
Including
These fractions are provided in separate vials to be mixed prior to use, and the solid fraction: liquid fraction weight: weight ratio ranges from 1: 1.2 to 1: 6.
The composition kit.   The composition kit according to claim 1, wherein the PDC has a degree of deacetylation in the range of 40-60%, preferably about 50%.   The composition kit according to claim 1, wherein the solid fraction comprises PDC in the range of 3-30% by weight, preferably in the range of 5-15% by weight.   The liquid fraction contains one or more acids selected from the group consisting of phosphoric acid, hydrochloric acid, ascorbic acid, lactic acid, acetic acid, formic acid, propionic acid, malic acid, citric acid and glutamic acid. The composition kit according to any one of the above.   The composition kit according to claim 1, wherein the liquid fraction has an acidity equivalent to at least 5% by weight of phosphoric acid.   The composition kit of claim 1, wherein the liquid fraction further comprises calcium hydroxide.   The composition kit of claim 1, wherein the weight ratio of the solid fraction: liquid fraction ranges from about 1: 1.3 to about 1: 4.   8. The composition kit of claim 7, wherein the weight ratio of the solid fraction: liquid fraction ranges from about 1: 1.5 to about 1: 3.   9. The amount of PDC in the range of 0.5 to 10% by weight, preferably in the range of about 1 to 5% by weight of the combined fractions, according to any one of claims 1-8. Composition kit.   The composition kit according to any one of claims 1 to 9, wherein the PDC is dissolved and precipitated.   11. The calcium phosphate comprises one or more of tetracalcium phosphate, [alpha] -tricalcium phosphate and other calcium phosphates capable of forming hydroxyapatite and / or brush stone precipitates. The composition kit according to any one of the above.   The composition kit according to claim 1, wherein the solid fraction contains sodium glycerol phosphate.   13. The composition kit according to any one of claims 1 to 12, wherein the composition begins to cure at room temperature after mixing and has a curing time in the range of about 15 to 30 minutes at room temperature.   The composition has 5 mL of B.I. 14. A composition kit according to claim 13, having a post-mix viscosity of less than 30N as determined by injectability when measured with a Braun syringe.   15. The composition of any one of claims 1-14, wherein the composition is free of bone morphogenetic protein or other biological factors selected from bone marrow, blood, bone and osteogenic protein. A composition kit according to 1.   The composition kit according to any one of claims 1 to 15, further comprising calcium sulfate in the solid fraction.   The composition kit according to any one of claims 1 to 16, which is sterilized by gamma irradiation.   Partially deacetylated chitin (PDC) with a degree of deacetylation in the range of 40-75% for use as a drug to repair and heal bone. A PDC having a degree of deacetylation in the range of 40-75% for use as a medicament according to claim 18, comprising:
The said PCD contained in the composition kit as described in any one of Claims 1-17. A method of healing bones,
A solid fraction containing partially deacetylated chitin (PDC) and calcium phosphate having a degree of deacetylation in the range of 40-75% and an acidic liquid fraction containing water and acid are 1: 1. Mixing together in a solid fraction: liquid fraction weight: weight ratio ranging from 2 to 1: 6 to form a mixture that is a liquid, semi-liquid or pasty cement mixture;
Applying the resulting mixture to a bone site to be healed;
Said method.   21. The method of claim 20, wherein the applying step is performed by injection.   21. The method of claim 20, wherein the applying step is performed by applying to the bone surface with a spatula or the like.   21. The method of claim 20, wherein the weight fraction of the solid fraction: liquid fraction ranges from about 1: 1.3 to about 1: 4.